1. Field of the Invention
The present invention relates to an organosilicon resin comprising recurring disilane units and having improved thermomechanical and waterproofing properties, a process for the preparation of such resin and the use thereof, in particular, as electrical insulation, molding powder, waterproofing agent, notably for textiles, and, more especially, as waterproofing agent for buildings, notably those constructed of masonry and concrete.
2. Description of the Prior Art
Organosilicon resins, including those comprising recurring disilane units, are known to this art, the process for preparation thereof being described, in particular, in the last paragraph on page 193 of Walter Noll, Chemistry and Technology of Silicones, Academic Press, 2nd edition (in English) (1968), and in U.S. Pat. Nos. 2,661,348 and 2,449,572.
According to such process, simultaneous hydrolysis and condensation of methylchlorosilanes and/or phenylchlorosilanes and/or methylphenylchlorosilanes are carried out in heterogeneous phase in the presence of an organic solvent immiscible, or very slightly miscible, with water which is present in excess, this solvent being a solvent for the starting material silanes and for the hydrolyzed and condensed silanes. The hydrolysis and condensation reaction is highly exothermic, and the reaction mixture is hence cooled. As solvent, there is generally used diethyl ether, dibutyl ether, white spirit, xylene, toluene and trichloroethylene.
The acidic water is decanted, the hydrochloric acid then optionally removed, for example, by washing the organic layer containing the resin until it is neutral, the organic layer is dried and the solvent then optionally removed.
There is thus obtained a partially hydrolyzed precondensed resin containing silanol groups, and this can be used as is and then cross-linked hot at a temperature of approximately 200.degree. to 250.degree. C. for applications such as molding powder, electrical insulator, and the like.
In the case where it is more especially required to use the resin as a waterproofing agent for masonry, it is also possible to isolate the resin from the reaction mixture in the form of a solution, which is generally diluted to 5 to 15% by weight and which can range up to 70% by weight of resin.
To improve the thermomechanical properties of these resins, it is known to add to the starting material alkylchlorosilanes phenylchlorosilanes, such as phenyltrichlorosilane or diphenyldichlorosilane, or phenylalkylchlorosilanes such as phenylmethyldichlorosilane. These silanes possess the major disadvantage of being much more expensive than the methylchlorosilanes which originate from the so-called direct synthetic process of Rochow, described in particular in U.S. Pat. Nos. 2,380,995 and 2,488,487, and which consists of reacting methyl chloride with a contact mass composed of silicon and copper at a temperature ranging from 200.degree. to 500.degree. C.
During this process, polysilanes are formed, and in particular chloromethyldisilanes, which are difficult to exploit commercially and technically.
It too has been proposed, in French Pat. No. 1,446,520, to hydrolyze its by-products in the absence of organic solvent and to incorporate them in building materials.
In French Pat. No. 1,081,726, there is described the preparation of organosilicon resins by hydrolysis and condensation of the entire crude residue of the direct synthesis boiling at 120.degree.-170.degree. C., or from the individual fractions boiling within certain temperature ranges. On page 1, right-hand column, last paragraph, and in Examples 2 and 4 of that patent, there is introduced the addition of, among other materials, dimethyldichlorosilane, respectively, to a polysiloxane residue boiling at 152.degree.-154.degree. C., and a crude residue boiling at 120.degree.-170.degree. C.
The resins obtained according to the teachings of the above-mentioned patent exhibit difficulties when they are used for waterproofing, and above all, cannot be obtained without entailing the appearance of microgels during the cohydrolysis. These microgels, which are insoluble in the organic solvents used, block the filters which are used to filter the decanted resin solutions, and this constitutes a major disadvantage in the industrial production of such resins. Furthermore, the presence of these microgels is an obvious cause of losses in starting materials, interferes with the decantation and prolongs the time required for the latter.